Common digital modulation is implemented by binary amplitude shift keying (2ASK), binary frequency shift keying (2FSK), binary phase shift keying (2PSK) and the like; and corresponding demodulation is implemented by filtering, envelop detection, local carrier multiplication, sampling decision and the like.
In a non-closed communication system, since a receiving end has no knowledge of the modulation mode of a transmitting end, a complicated demodulation circuit needs to be configured in order to prevent interference caused by other modulated signals to modulated signals that need to be demodulated.
Referring to FIG. 1, in a typical 2FSK demodulation method, four filters, two envelop detectors and one sampling decider need to be configured in order to prevent interference caused by 2ASK, 2PSK and other modulated signals to the 2FSK modulated signal. This demodulation method is very complicated, and implementation of this method requires a large circuit area and high power consumption. Therefore, this method fails to accommodate application of ultra-low power consumption. In a closed communication system, since the receiving end acknowledges the modulation manner of the transmitting end, including amplitude, frequency, length and the like information of the carrier, the receiving end may only receive a specific type of modulated signals. Therefore, unlike the scenario of a non-closed communication system, it is unnecessary to consider interference caused by other modulated signals like.
As seen from the above, a closed communication system has the characteristics of single communication signal, fixed modulation manner, and limited power consumption. If the signal demodulation apparatus in a conventional communication system is applied to a closed communication system, an apparatus with a complicated circuit needs to be further configured, which consequently increases power consumption of the communication system.
Therefore, a signal demodulation apparatus in a closed communication system is urgently desired to solve the problem in the related art.